The present invention relates to methods of recovering devices from a fluid medium, and more particularly to recovering buoys from water by using a grapnel deployed from a helicopter or ship.
Heretofore, recovery of a buoy from the water by a helicopter has been extremely difficult requiring the lowering of a man from the helicopter to attach a line to the buoy. Recovery of mine countermeasures gear, as well as buoys, has generally been accomplished exclusively by ship. Buoys are generally secured in position by a chain or cable which connects the buoy to an anchor. Current recovery techniques involve maneuvering a ship alongside the buoy to be recovered and hooking it with a shepherd's hook, or deploying a small boat to tow a line to the buoy. Other methods have used hooks towed behind a boat to hook the buoy mooring cable to move the buoy to a new location. In higher sea states (sea state three and higher) it is extremely difficult and hazardous to recover buoys, and it is an established fact that ships cannot recover buoys in sea states exceeding sea state three due to the hazard to personnel.
Since buoys are used extensively as navigational aids and as markers for the location of various underwater objects, it is desirable to have a method for recovering and relocating buoys without manual intervention, with its attendant risks.